© Nick Moir
Kindergarten students enjoying a laugh. A child disinclined to join in could have signs of psychopathic traits.
Boys who have personality traits associated with psychopathy do not laugh along with other children, new research has found.

When exposed to laughter, the boys at risk of developing psychopathy reported less interest in joining in and showed less activity in the emotional centre of the brain.

The study's lead researcher Essi Viding said such children did not experience the world in the same way as other children.

"That does not mean that these children are destined to become antisocial or dangerous," she said. "Rather, these findings shed light on why they often make different choices from their peers."

The study, carried at University College London, measured the brain activity of 62 disruptive boys and 30 normally-behaved boys.

A child was flagged as having traits associated with psychopathy if they were disruptive (aggressive and difficult to control) and "callous-unemotional" (lacking empathy and emotion).

It should be noted the researchers were not saying some of the children involved in the study were psychopaths, only that they displayed traits that could influence a diagnosis in adulthood.

"It is not appropriate to label children psychopaths," Professor Viding said. "Psychopathy is an adult personality disorder."